Dental prosthetic



Sept. 28, 1937. F. D. SNELL 2,094,308

DENTAL PROSTHETIC Filed Feb. 12, 1935 attorney Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE 6 Claims.

This invention has utility as an improvement in dental prosthetics.

The term prosthetic dentistry as used hereinafter designatesthe making of sets of teeth or parts of such sets for either or both jaws, filling ofcavities in teeth, and building up broken crowns of one or more teeth. I

The usual completeprosthetic process of making sets of teeth involves making of wax negative of the gums and roof of the mouth, if the upper jaw is the one to be supplied, or of the gums alone, if the lower jaw, making from this a positive impression in the material which is to form the plate, usually a vulcanizable substance, fixing the teeth in this plate, and vulcanizing it. y 7

It is usually the case that this process involves a deal of grinding of the finished plate before it becomes comfortable.

The complete process of filling a; tooth involves clearing decaying matterand infectious matter from the cavity, and forcing, often by hammer blows, the filling into the cavity, all of which is annoying and time consuming.

My invention relates to the making of the positive from which the inlay or plate can be made by any well known process, andonly this portion of the process is described and claimed.

The term positive as used herein designates a structure one of whose surfaces is an exact replica of the shape and markings of the gums or of a part thereof, of the gums and roof of the mouth, of a cavity of a tooth or of the surface of the broken portion of a tooth or teeth.

The term negative as used hereinbelow desl'gnates a structure which will exactly fit into the cavity of a tooth or upon a broken crown, or upon the gum and the roofof the mouth.

An object of the invention is a process by which a positive of the exact size and shape of a cavity in a tooth can be produced, from which positive an inlay for the cavity can be fabricated by methods well known in the dental art.

Another object of the invention'ls an adaptation of the above process by which positives of broken crowns of one or more teeth can be pro duced, from which positives the missing portions of such crowns can be fabricated by well known methods.

Another object of the invention is a modification of this process by which a positive of the gums of the upper jaw, or of the gums and roof of the mouth can be produced, from which positive the usual sets of teeth can be fabricated by well known processes.

ing material in the cavity, the shaping of the parts of the cavity as completely as possible.

can be fabricated.

Still further objects of the invention are the positives above described, as articles of manufacture. I

LThe invention accordingly comprises the several steps and therelati'onof one or more of the steps with respect to each of the others, and the articles possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. I A

The usual process of filling a cavity in a tooth involves a clearing out of the decayed or decay-k cavity so that it shall hold the filling tightly in place, then forcing the filling material into t cavity using force enough to cause it to fill This involves the use of considerable pressur and even tapping of the material and the process is annoying, sometimes painful, and often results in fracture of the remaining crown. It is also time consuming for the patient, especially when several teeth are to be filled at once. 5

A more sightly and more satisfactory method of filling a cavity is to so shape the cavity that it is not undercut, form a metal inlay to approximately fit the cavity and by suitable adjustments by grinding and otherwise complete the fitting 40 of the inlay to the cavity. While methods of reproduction of the cavity by ramming of dental amalgam against a wax impression are fknown, they are not satisfactory and their use by the profession is attended by serious'inconvenience and dissatisfaction both to the operator and the patient, due to failure to accurately reproduce in the extended process necessary the exact form and size of the cavity in the inlay con-ff structed therefor. By the process of myinvention a positive of the cavity is constructed and thereafter the inlay fabricated therefrom by methods now well i known to the profession, all this in the laboratory, and in the absence of the patient. When 55 the inlay is completed, it fits perfectly into the cavity, and its insertion and securing occupies but a short time.

By the use of standardized burrs, so that the cavities of the same size and shape can be made in teeth, it will be possible to make standardized inlays, which can be kept in stock, ready for insertion as soon as the cavity is shaped and disinfected, thus saving a great deal of time over present processes, and several trips to the dentist's office, as is at present necessary.

In case the whole or a portion of a crown of a tooth has been broken away, in accordance with my invention, the broken surface is cleaned and disinfected, and shaped properly to hold a replacement of the broken portion, a positive of the broken surface is prepared, and from that the missing portion of the crown fabricated. Its placement upon the tooth is then a very short process.

In this way the very annoying unpleasant and painful manipulations involved in the aflixing of gold or porcelain crowns by present processes, are avoided.

In the accompanying drawing I have indicated, somewhat diagrammatically, one manner of carrying out my process, and variations thereof.

It is to be understood, however, that the drawing is intended by way of illustration only, and not by way of limitation.

In the drawing:

Figure 1 indicates a band used in the performance of my process.

Figure 2 is a view, from below, hereinafter called a face view, of a tooth of an upper jaw, having a cavity and with the band attached.

Figure 3 is a perspective view of the same tooth having its crown surrounded by the band and the cavity in the tooth together with the projecting portion of the band filled with a plastic mass, the crown, band, and the plastic filling being shown in section.

Figure 4 shows, in vertical section, the plastic negative of the cavity in Figure 3, surrounded by the band, and the plastic negative carrying two layers of metal electro-plated thereon.

Figure 5 shows, in the same cross section, the completed positive of the cavity. This is a final product of my process.

Figures 6 to 9 correspond to Figures 2 to 5, re-

spectively, except that they deal with four teeth, three of which have broken crowns.

Figure 10 is a perspective view of the wax Figure 11 shows, in vertical cross section, the

wax negative of Figure 10 carrying two layers of electro-plated metal thereon.

Figure 12 is a cross sectional view of the electro-plated negative of Figure 11, mounted in a band, thus forming a shell, the bottom of which is the copper plate.

In this drawing, I is a deformable band of electricity conducting material, preferably of cop per, but lead, silver, gold, or any metal or alloy of metals of sufilcient deformable rigiditywill sufiice. These bands are made in sets of different diameter and thickness, to fit teeth of difl'erent size and length, and they must be thin enough to slip between adjacent teeth. They must have sufficient rigidity to maintain their shape, but be flexible enough to permit of deformation to fit the irregular crowns, and to be pressed between adjacent teeth as shown in Figure 7.

After a cavity has been cleaned and shaped, and it is noted here that it must not include any undercut, and disinfected, one of these bands is fitted tightly around the crown, and pushed down so far as to close any opening of the cavity on the side of the crown.

A low fusing point plastic material, the well known molding wax used by dentists being preferred, is then forced into the cavity so as to fill it completely and tightly, and to extend in the band a sufiicient distance to give this mass a proper strength for the manipulations hereinafter described. The band with its contents and the negative of the cavity is then removed from the tooth.

It should be noted that the plastic mass, called hereinafter wax, to avoid circumlocution, forms I terial, such as metallic powder, or graphite, tak-' ing care that this material also makes good contact with the metallic band. The inner and outer surfaces of the band are then coated with some non-conductor, such as a coating of shellac, and the assembly of band, negative and hook is then suspended by hook I 5, as cathode in an electro- .plating solution.

This solution may be composed of any metal which yields itself to the purposes of this process, but I have found a solution of the following composition satisfactory:

Water cubic centimeters '2000 Nickel sulfate. hexahydrate ..grams 140 Ammonium chloride do 11 Boric acid solution cubic centimeter-5.- 55

The boric acid solution contains 3.3% boric acid and has its pH adjusted to 5.6.

The assembly is allowedto remain in this solution from three to twenty-four hours or until the nickel has been deposited on the negative to a suflicient thickness, at a current density of approximately 0.2 to 1 ampere per square decimeter.

As one specific embodiment of my invention when the nickel plate has become of proper thickness, the assembly is removed from the nickel electrolyte, washed, and suspended in a bath having the following composition:

Water. cubic centimeters 1000 Copper sulfate pentahydrate grams 200 Sulfuric acid, of 98%--. do 50 Neither of these solutions differ markedly from those ordinarily used in nickel and copper electro-plating, the strength is not at all critical, and any ordinary solution of these electrolytes may be used. Further, except in certain special uses of the invention, it is not necessary to use two different metals. Thinness of metal plating is essential since that is the reason faithful reproduction is obtained.

The product of this step is shown in Figure 4, where H is the negative of the cavity made of the plastic material 6 and 1 and 8 respectively, are the nickel and copper coatings.

Now the portion of the interior of the band I is coated with graphite to prevent adhesion of the metal next to be used, and the cavity seen at the top in Figure 4 is filled with a material which cement, either is sufiiciently plastic to enter into all the minute irregularities of surface of the copper plate, and then to set into a rigid mass. This material, when set, must also adhere tightly to the copper plate. This material may be of a plastic that ordinarily used by dentists, or of other material of like nature. a

This material" may also be of low melting point metal or alloy of metals, of which many varieties are known, but I prefer Woods metal because of its low melting point, and of its fluidity when melted.

This step is cited in the claims as backing of the electro plate, whether the material used be a plastic cement or a metal.

If a low melting point alloy be used, its heat will melt the wax, leaving the surface of the nickel positive clean. If other material be used, the wax must be cleared off the nickel by other processes.

The product of this process is shown in Figure 5.

From this positive, an inlay which will accurately and completely fill the cavity in the tooth can be fabricated by methods well known to those skilled in the art.

FigureslO, 11, and 12 show a variation in the process as above described, in which the wax negative 6 shown in Figure 3 is removed from the band, and from the cavity, and, as shown in Figare 10, a wire l3 has been inserted from the back of the wax, to a point flush with the cavity surface of the wax negative, and this negative surface is coated with an even coat of electroconductive material, either metallic powder or graphite, with which the end of the wire also must make good contact. This wire I3 is inserted through the wax without distortion by slightly warming it, or it may be'inserted into the cavity efore the wax has been forced to fill it.

The outer end of this wire carries hook l5, by

means of which the negative is suspended in electrolyte baths as described above to receive its coat or coats of metal. The product of this modification of my process is shown in Figure 11, in which figure the reference characters have the same significance as in Figures 2 to 5.

Conductive band I is then placed around the nickel-copper plates as shown in Figure 12, in such a manner that the band forms a cell, whose bottom is the copper plate. :The inside of the band is then thoroughly coated with graphite or other material which will prevent molten material adhering thereto, such as talcum or chalk, and

the cell filled with alloy or plastic materials already described. The wax is removed either by the heat of the molten material, or otherwise, and the final product is that shown in Figure 5 as obtained by the first modification of my invention.

Figures 6 to 9 illustrate another modification of my invention where a plurality of adjacent teeth, four being'shown in this instance, are to be repaired. f

In this case, the band i is large enough to surround all the teeth, and is tightened upon them by bending it inward between adjacent teeth, as shown at I4 in Figure 7.

Subsequent manipulations follow exactly the steps already outlined, following either the process illustrated by Figures 2 to 5 or 10 to 12, the

final product in either case being shown in Fig-- ure 9.

It is deemed unnecessary to draw separate figures for the modification of the process illustrated in Figures 10 to 12 as applied to a plurality of teeth, or to burden this specification with minute descriptions of these modifications such as by taking an impression of several teeth in plaster or wax in an impression tray according to technique well known to the dental profession.

A modification of this process can be used in making sets of teeth for either or both upper and lower jaw. In either case a negative wax or other impression is taken just as at present practised, the negative surface of this impression coated with graphite or other suitable material as stated above, and suspended as cathode in a nickel -cetrolyte, then in a-copper bath, until the respective nickel and copper plates have attained the desired thickness, by which the nickel plate becomes the positive of the portion worked upon. This assembly of metallic plates is then made the bottom of a cell with a metallic band as described above, the copper being the inside bottom of the cell, and this cell=is filled with plastic material or with molten metal of low melting point all as already described.

When the wax is removed, the nickel is an exact positive of the area molded, and from that cient portion of the roof of the mouth, if the missing tooth is an upper one, the surface of this is electroplated as described above, backed by plastic material or low melting point metal or alloy, thus forming a perfect positive, from which the plate and its attached tooth can be fabricated by those skilled in the art.

Here also, it is deemed unnecessary to encumber this specification with detailed descriptions of the steps of my invention as applied to this case. One skilled in the art will understand how to apply them.

From this detailed description ofmy invention it is seen that it is a great improvement over present processes. It avoids the annoyance in separable from the hammering of the filling into a cavity, or fitting an inlay to the cavity, and saves a great deal of time to a patient in several visits to the dentists ofiice. Moreover, it is-impossible to be certain that a filling inserted in the usual way completely fills all parts of the cavity,

and when it does not do so, these vacanciesbecome the seat of new infection and decay.

-Also, in the various modifications described its superiority is seen. In mechanical working, a wax or plaster impression of a cavity or of the roof of the mouth or of another area easily becomes scratched, marred, or deformed. When so altered all further work with it faithfully repro- .duces the imperfections instead of the original Instead bythe electrochemical process described a'firm metal surfaced reproduction is first produced and then 'by working with this it is possible for those skilled in the art to produce by known methods faithful negative reproductions such as of inlays for cavities or of plates for the art.

In contrast, by my mouth. When the positive reproduction has been produced by my process it will stand mishandling and abuse such as would destroy the corresponding wax or plaster positive.

Since certain changes in carrying out the above process, and certain modifications in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not. in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim: I

1. The steps in a process of prosthetic dentistry which comprise surrounding a tooth having a cavity with a closely fitting metallic band which extends beyond the crown, filling both cavity and band with plastic material thus forming a negative of the cavity, removing band and plastic material without relative permanent displacement, rendering said negative surface electrically conductive, electrolytically coating the cavity fitting surface of it with metal, backing this metallic coating with plastic material and thereafter removing the first named plastic material whereby the free surface of the metallic coating becomes a positive of the cavity, from which an inlay may be manufactured by methods well known to those skilled in the art.

2. The steps in a process of filling a cavity in a tooth which comprise placing a closely fitting metallic band around the crown of said tooth, tightly filling the band and cavity with molding wax already in use by dentists, removing the band and wax negative without relative permanent displacement, completely and smoothly coating the cavity-facing surface of said negative with a conductor of electricity which conductor 'must be in electric contact with the band, coating all exposed surfaces of the band with non-conducting material, electrolytically forming a metallic coating of suitable thickness upon said cavity-fac+ ing surface of the negative, backing the said metallic coating with rigid material and removing the molding wax, whereby the exposed surface of the metallic coating becomes an exact copy or positive of the cavity in the tooth, from which an inlay may be constructed by methods well known to those skilled in the art.

3. The steps in the process of filling a cavity in a tooth which comprise placing a closely fitting metallic band around the crown of said tooth, tightly filling the cavity and band with molding wax of the type already known to dentists, removing the band and wax without permanently disturbing their relative relations, coating the cavity-facing surface of the wax with finely divided electricity conducting material, which must be worked into close electric contact with the metallic band, attaching a wire to the band in any convenient fashion, covering the band and wire with nonconducting material, suspending this assembly as cathode in a nickel electrolyte, depositing upon the cavity facing surface of the wax a coating of nickel of suitable thickness, then placing the assembly in a copper electrolyte as cathode, and depositing a copper coating upon the nickel, backing the copper plate with a lowmelting point metallic substance, and removing the wax from the nickel plate, and the band from this assembly, whereby the nickel becomes an exact replica of the cavity.

4. The steps in a process of prosthetic dentistry as applied to a tooth or a plurality of teeth having defective crowns which comprise surrounding the tooth or teeth with a closely fitting metallic band, filling the band and the defective portion of the crown with a plasticmaterial and forcing it into contact with all defective portions of the crowns thus forming a negative of said portions, removing both band and plastic material without permanent relative displacement and without distortion of the plastic material, rendering said negative surface electrically conductive, electrolytically forming a metallic coating of suitable thickness upon the said negative, arranging this metallic coating and the plastic material as the bottom of a metallic cell, the plastic material on the outside thereof, filling said cell with a material which forms a rigid mass with the said coating and removing both the wall of the cell and the plastic material whereby the exposed face of the metallic coating becomes an exact positive of the surfaces of the broken crown.

5. In the process of prosthetic dentistry which involves the formation of a mold of a defective tooth and building an inlay thereupon, the steps which comprise surrounding su'ch tooth with a closely fitting band which extends beyond the crown of the tooth, filling both the defect and band with plastic material, whereby a portion of the band projects from the negative surface to form a cup the bottom of which is a negative of the-defect, removing the band and plastic material without relative displacement, rendering said negative surface electrically conductive, electrolytically coating it with metal, applying to the metallic coating sufiicient plastic material withinthe cup to form rigidity and thereafter removing the flrst named plastic material, whereby the free surface of the metallic coating becomes a positive of the defect from which an inlay can be manufactured by methods well known to those skilled in the art.

6. In a process of prosthetic dentistry which involves the formation of a mold of a defective tooth and building an inlay thereon, the steps which comprise placing a closely fitting metallic band around the crown of said tooth, filling both defect and band with molding material of the type well known to dentists, removing said material and band without disturbing their relations, coating the defect facing surface of the molding material with finely divided conducting material, working this material into intimate contact with the band, attaching a wire to the band, covering both wire and band with insulating material, suspending this assembly by means of the wire in a nickel electrolyte, depositing upon the prepared conducting surface a thin coating of nickel, and then upon the nickel a coat of copper, backing the copper coat with a low melting point alloy and removing the molding material, whereby the surface of the nickel coat is an exact duplicate or positive of the defect, and can be used to construct an inlay.

FOSTER DEE SNELL. 

